Twenty Ten; how to change color around posts

Hi everyone, i would like to change color only to the area around the posts, the result hopefully being any post looks like a single white sheet of paper. If you give a look to my blog this may support my cranky explanation.

t-p: thank you for suggesting Firebug. At first sight it seems to be a sophisticated tool for developers, but gotta tell you I am an old dog and this trick is way too new for me. Call me lazy arse if you wish, but i believe I need a step by step, fool proof instructions before I retire…
Thank you anyway, I appreciated.
S.

Thank you again to t-p and Andrew Nevins.
Help somenone else who is simply willing to suggest a few lines of code (provided this can be done with my particular request) as I see it is commonly used here, without feeling insulted.
Humbly.
S.

t-p; I do have a child theme. I would not be able to do it again, but I have it. “wrapper” was probably the word addressing the area I was trying to find out and change. I will copy and paste your code and see what happens. The background controlling thing, yes I have used it, that’s perfect for dummies like me but it would change a larger area.

Anyway thanks a lot, I am trying to reach for my goal with your instructions and if I fail it means I am hopeless.

PS I’ve been playing around with the Firebug thing; it’s a fantastic tool, but it’s too far ahead for me to use it.